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Abstract

Conventional endoscopy has allowed examination and sampling of the mucosal layer of the gastrointestinal tract. Conventional ultrasonography allows transcutaneous examination of abdominal viscera. Endoscopic ultrasonography (EUS), or endosonography, is a combination of endoscopic and ultrasound technology, where the union is greater than the sum of its parts. As a result, EUS allows imaging and intervention beyond the mucosal layer of the gastrointestinal tract and its reach extends to the mediastinum, liver, adrenals, pancreatobiliary system, intra-abdominal lymphatic system, and peri-rectal tissues. EUS is at the forefront of advances in endoscopic innovation and has become a particularly indispensable tool in the staging of gastrointestinal and pulmonary malignancies.